The invention relates to an internal seal for the piston of a rotary piston engine including a slide ring having an annular scraping edge. The ring is of L-shaped cross-section with an axial flange and a flange extending radially outward.
In pistons of the type described, the function of the internal seal, arranged in an annular groove, is to seal the rotating piston against the face of the end part so as to prevent passage of coolant or lubricant radially outward along the face into the working chamber. For this purpose, the internal seal has a slide ring with a scraping edge, generally made sharp-edged radially inward and provided with a somewhat beveled relief radially outward. The function of the ring is essentially to pass over any oil adhering to the face in the centrifugal motion of the scraper ring radially outward and to scrape it off and feed it back radially inward in the centripetal motion.
Now it has been found, however, that the sharp scraping edge in contact with the face in known slide rings, especially during unavoidable periods of running cold, will be ground down to an annular area in the course of time. A scraping edge ground down in this way will impair the scraping action very substantially with the result that the slide ring can float on the oil adhering to the face in both its outward and inward radial motions, so that the slide ring ceases to perform its proper function satisfactorily, and oil consumption is increased.